function show(foo) {
        document.getElementById(foo).style.display="block";
        document.getElementById("i"+foo).src="/cat/img/tree_collapse.gif";
}
function hide(foo) {
        document.getElementById(foo).style.display="none";
        document.getElementById("i"+foo).src="/cat/img/tree_expand.gif";
}
function toggle(foo) {
        if( document.getElementById(foo).style.display == "block") {
                hide(foo);
        } else {
                show(foo);
        }
}